The electrotherapeutic treatment of cardiac arrhythmias by means of implantable cardiac pacemakers has become established as a powerful, versatile, comparatively low-risk and reliable form of treatment. Electromedical implants of that kind include numerous functional individual components which are necessary for long-lasting therapeutic treatment of the heart, which is suited to the physiological factors involved and which is as trouble-free as possible. Those components can be systematically divided into components which are disposed in a housing of the implant and components which are arranged outside the housing. The latter involve for example sensors for physiological parameters and the electrodes, by way of which a pacemaker pulse is transmitted to the atrium or ventricle myocardium. The implant housing in contrast accommodates functional components such as a battery, a circuit, telemetric means and the like.
The electromedical implant is to have a service life which is as long as possible and good compatibility. Under some circumstances those two aspects can be in conflict. Thus on the one hand the implant should be of the minimum possible structural size so that it is not perceived as troublesome by the patient after the implantation operation or indeed give rise to unwanted physiological reactions. On the other hand the battery for a long service life must be of the maximum possible capacity, which in a practical context means that the battery generally fills up markedly more than 80% of the internal space of the housing. There is therefore always the need for making the optimum possible use of the available space.
As intracardial therapy in the meantime has developed into a standard procedure which has proved its worth worldwide millions of times, it is appropriate for cost reasons to automate the process for production of the implants. The construction of current electromedical implants can in that respect be described in simplified terms as follows. All functional components such as the battery, the circuit, the telemetry unit or the like are disposed in mutually juxtaposed relationship in the implant housing. The implant housing itself is generally of a flat, elongate contour with rounded-off edges and is generally formed from two half-shell portions with a kind of snap-action mechanism comprising interengaging edges. Then, in the opened condition, the conventional arrangement with functional components mounted in mutually juxtaposed relationship on an inner base surface of the half-shell portions can be clearly seen. It will be noted that such an arrangement suffers from the disadvantage that, in assembly of the individual components, it is necessary to operate on a plurality of production axes. That makes automation more difficult and leads to increased costs. In addition the available space cannot be put to optimum use, for example because generally an expensive and complicated electrical contacting means for contacting the power-consuming components with the battery additionally has to be fitted.
U.S. Pat. No. 6,026,325 to Weinberg et al. discloses an electromedical implant having a circuit whose electronic components are arranged in stacked relationship. The individual electronic components of such a circuit are disposed perpendicularly to the heightwise extent of the implant housing on parallel substrate planes. The circuit and the further functional components such as a battery and capacitors are mounted in conventional manner in mutually juxtaposed relationship on the base surface of the implant housing.
U.S. Pat. No. 6,251,124 to Youker et al. describes a cardiac pacemaker in which a plurality of capacitors is arranged in a plurality of substrate planes in the housing. All further functional components—disposed beside the capacitors—are arranged on the inner base surface of the housing.
Furthermore, WO 99/06107 discloses a cardiac pacemaker whose circuit includes a memory unit comprising memory chips stacked in mutually superposed relationship. That is intended to minimize the structural space required for an electrical connection between the individual memory chips. As in the above-mentioned specifications, the stacked arrangement is limited to selected partial structures of the functional components of the implant.